The present invention relates to medical apparatus, and particularly to medical devices adapted to be implanted into a subject""s body and to be magnetically-coupled to an external drive magnet.
Medical apparatus is known comprising an external drive magnet mounted for rotation externally of a subject""s body; an implantable driven magnet configured and dimensioned to be implantable in the subject""s body and mounted for rotation by magnetic coupling with the drive magnet when the driven magnet is implanted in the""subject""s body and the drive magnet is rotated externally of the subject""s body sufficiently close to the implanted driven magnet to be magnetically coupled thereto; and an implantable device mechanically coupled to the driven magnet to be driven thereby. Examples of such apparatus are described in U.S. Pat. Nos 4,575,158 and 3,810,259, both relating to an implantable pump for controlling urine flow.
In such apparatus, the two magnets rotate about the same axis (i.e., the two rotary axes are collinear) such that the magnetic poles of the two magnets are continuously coupled by the magnetic field, and thus the operation of the two devices is analogous to a mechanical clutch.
An object of the present invention is to provide medical apparatus of the foregoing type but having a number of advantages, as will be described more particularly below.
According to the present invention, there is provided medical apparatus of the foregoing type characterized in that the driven magnet is mountable for rotation in the subject""s body about an axis of rotation which is not collinear with the axis of rotation of the external drive magnet such that the magnetic poles of the external drive magnet are magnetically coupled sequentially with the magnetic poles of the implanted driven magnet to rotate the implanted driven magnet, thereby providing flexibility in the location, design and dimensions of the implanted driven magnet, and in the speed and torque ratios between the two magnets.
As will be described more particularly below, the basic concept of the present invention, to implant the driven magnet about an axis for rotation which is not collinear with the axis of rotation of the external drive magnet such that the magnetic poles of the external drive magnet are magnetically coupled sequentially with the magnetic poles of the implanted driven magnet, produces an operation which is analogous to a xe2x80x9cgear couplingxe2x80x9d, rather than a xe2x80x9cclutch couplingxe2x80x9d of the prior art. Such an operation permits a wide flexibility in the location, design and dimensions of the implanted driven magnet, and in the speed and torque ratios between the two magnets.
For example, where the implanted devices are to be used in a pump for urinary control as in the above-cited US patents, the driven magnet may be implanted in the urethra of the subject and elongated in the direction of the urethra so as to increase the torque coupling between the drive and driven magnets In addition, the implanted driven magnet may be provided with a smaller number of poles than the external drive magnet, which, although decreasing the torque ratio between the two magnets, correspondingly increases the speed of rotation of the implanted driven magnet analogous to the manner of increasing the speed ratio in a gear coupling according to the xe2x80x9cgear ratioxe2x80x9d.
The high degree of flexibility in the location, design and dimensions of the implanted driven magnet provided by the above arrangement permits the device to be used in a large number of medical applications. Described below are implementations of the invention in the form of an artificial pump, e.g., for implanting into the urethra of a subject""s body to pump urine from the bladder, for implantation into the aorta of a subject""s body to pump blood (to assist a failing or recovering heart), or for implantation into another blood vessel of the subject""s body, e.g., to aid blood circulation in an ischemic leg.
Other applications described below include an artificial valve to serve as an artificial sphincter, a generator for recharging an implanted battery, and a bone-stretching device.
Further features and advantages of the invention will be apparent from the description below.